/Engine/Source/Runtime/CoreUObject/Public/Misc/PackageName.h
Checks if the package exists on disk. PackagePath must be a mounted path, otherwise returns false
true if the specified package name points to an existing package, false otherwise.
static bool DoesPackageExist ( const [FPackagePath](API\Runtime\CoreUObject\Misc\FPackagePath) & PackagePath, bool bMatchCaseOnDisk, [FPackagePath](API\Runtime\CoreUObject\Misc\FPackagePath) * OutPackagePath )